Method of treating cellulose compounds



Patented July 7, 1925. p

JOHN COLLINS GLANCE, OF PROVIDENCE,-RHODE1ISLAND, AS SIGNOB TO THE NITRO- GEN CORPORATION, ISLAND.

OF PROVIDENCE, RHODE ISLAND, A CORPORATION OF BHODE HETHOD OF TREATING GELLULOSE COMPOUNDS.

No Drawing.

To all whom it may concern:

Be it known that I, J OHN COLLINS CLANoY, a subject of the King of Great Britain, residing at Providence, in the countyof Providence and State of Rhode Island, have invented certain new and useful Improvements in Methods of Treating Cellulose Compounds, of which the following is' a specification.

This invention relates to an improved .method of treating cellulose compounds, and has to do more particularly with the use of an improved solvent for cellulose esters and the formation through the instrumentality of said solvent of a cellulose compound possessing certain new and useful properties which adapt it for wide use in the arts.

While it'is known that certain celluloseesters, such for example, as certain of the acetates and nitrates, are soluble in substances such as acetone, amyl acetate, tetrachlorethane and carbon bisulfid, the use of certain of these substances is open to objections such as, the cost of the solvents, their inflammability, their poisonous nature and the difliculty experienced in removing the solvents from the final product. Moreover, by no means all of the cellulose esters are soluble in any of the solvents named, and each of the above solvents is adapted for use with only an extremely limited number of the celluloseesters included in the classes mentioned above.

One object of the present invention is to provide a novel solvent for cellulose esters, including particularly the acetates and nitrates, which is capable of more general use than those heretofore employed, which is not inflammable and which is capable of being readily separated from the resultant product.

Other objects and advantages of the invention relate to certain novel steps and combinations of steps involved in the carrying out of the invention as well as certain methods of treatment which will be more.

fully set forth in the detailed description to follow.

Ihave found that liquid sulfur dioxid serves as an excellent solvent for the cellulose esters generally, being capable of dissolving a considerably greater number of the acetates and nitrates of cellulose than any of the solvents heretofore generally employed,

Application filed November 21, 1921. Serial No. 516,597.

dioxid cellulose acetates and nitrates can be dissolved so as to continue to possess the structural aggre ates of the original cellulose, acetates an nitrates, that is, without I being degraded, thus forming a cellulose compound capable of being given any desired shape while at the same time retaining the strength inherent in the original cellulose structure. I propose to place the cellulose esters, such as cellulose acetates, in a bath of liquid sulfur dioxid, whereupon I find that they immediately dissolve to form a clear solution which can be readily freed from air bubbles or entrained gases, and the solution thus formed may be caused to flow upon an endless belt, forced through minute apertures or placed in moulds and the sulfur dioxid freed from the mass by evaporation to form a transparent or translucent film, thread or other desired shape possessing a high degree of strength and capable of use for a variety of purposes.

Since sulfur dioxid is liquefied only at comparatively low temperatures unless subjected to pressure in excess of that normally exerted by the atmosphere, I prefer to dissolve the cellulose esters in the sulfur dioxid under a pressure somewhat greater than that normally exerted by the atmosphere and suflicient to maintain the sulfur dioxid in a liquid state, thus making it unnecessary to employ such low temperatures as would be inconvenient in practical operation. The sulfur dioxid .is then removed from the resulting product by lowering the pressure and if necessary raising the temperature to hasten the evaporation of the sulfur dioxid from the mass. However, the liquid sulfur dioxid may be employed under atmospheric pressure by sufiiciently lowering the temperature and the cellulose esters dissolved therein, whereupon the sulfur dioxid may be substantially removed from the mass by raising the temperature or if desired by subjecting the mass to a pressure somewhat lower than that normally exerted by the atmosphere, or

increased temperature and reduced pressure The product-obtained by directly dissolving the cellulose esters in liquid sulfur dioxid under pressure and evaporatlng oif the sulfur dioxid in a closed system where no moisture is present, is considerably tougher, more elastic and more clear than that obtained by evaporting off the sulfur dioxid in the open air.

The sulfur dioxid employed is preferably substantially pure and free from moisture or other contaminants, and may of course be recovered if desired when removed from the resultant product.

Having found that the nitrates of cell ulose as well as the acetates are soluble in liquid sulfur dioxid as above described, I may utilize liquid sulfur dioxid for dissolving either cellulose acetates or cellulose n1trates separately or may mix cellulose acetates and cellulose nitrates in any desired proportion and dissolve the mixture in sulfur dioxid to obtain a cellulose compound possessing certain desired qualities when the solvent has been removed.

The product resultin from the treatment of cellulos esters as aimve described possesses certain qualities which admlrably adapt it for use in the arts by reason of the readiness with which the solvent may be freed from the resultant product as well as by reason of the fact that certain of the cellulose esters not generally soluble in solvents heretofore commonly employed are soluble in the sulfur dioxid thus imparting to the resultant product a structural strength not heretofore readily obtainable.

I have also discovered that while liquid sulfur dioxid dissolves the cellulose esters of itself without the addition of an other solvent, it also possesses the partlcularly novel function of rendering cellulose esters soluble in liquids which are not otherwise solvents therefor. Among such liquids are carbon-tetrachloride, pentachlorethane, dichlorethane, gasoline, benzine, turpentme and chlorinated oils, such for example as chlorinated benzine, chlorinated naphtha-' lene, chloriiated kerosene, chlorinated heavy mineral oils and the like.

In effecting the solution of the cellulose esters in the above substances I first dissolve the esters in liquid sulfur dioxid and then add one or more of the liquids enumerated above to the solution and evaporate ofi the sulfur dioxid leaving the cellulose ester which remains in solution in the added menstruum. p

I preferably form the menstruum to which the esters are transferred by mixing one or more of the partial solvents such as carbon tetrachloride, pentachlorethane or dichlorethane with one or more of the nonsolvents such as gasoline, benzine, turpenpheric pressure until the solution of cellulose ester in hquid sulfur dioxid is transferred into the other menstruum, when the evaporation of the sulfur dioxid from the mixture may be effected in the open air or under reduced pressure, that is, sub-atmospheric pressure.

"This feature of the invention is of great importance since it makes it possible to prepare a solution of cellulose esters in liquids not otherwise solvents for the same, and liquids of different boiling points may be utilized.

As illustrations of important commercial applications of the invention the dissolved esters may be utilized in the manufacture of photographic films, artificial silk and the like, while the solutions formed by the substitution of the liquids enumerated for liquid sulfur dioxid may be employed for a variety of purposes such as forming transparent or translucent coatings and films upon surfaces.

Having described my invention, claim is:

1. The process which comprises, dissolving a cellulose ester in liquid sulfur dioxid.

2. The process which comprises, dissolving cellulose acetate in liquid sulfur dioxid.

3. The process which comprises, treating a cellulose ester with liquid sulfur dioxid to dissolve the same, and then substantially removing the sulfur dioXid from the compound formed.

4. The process which comprises, treating cellulose acetate with liquid sulfur'dioxid to dissolve the same, and then treating the mass to substantially remove the sulfur dioxid therefrom.

5. The process which comprises, treating a cellulose ester with liquid sulfur dioxid to dissolve the same, and then substantially removing the sulfur dioxid therefrom under a pressure less than that at which the solution was effected.

6. The processwhich comprises, treating cellulose acetate with liquid sulfur dioxid to dissolve the same, and then substantially removing the sulfur dioxid therefrom under a pressure le'ssthan that at which the solution was effected.

7. The prOcessWhich comprises, treating what I a cellulose ester with liquid sulfur dioxid to dissolve the cellulose ester, and then substantially removing the sulfur dioxid therefrom with exclusion of moisture.

8. The process which comprises, treating cellulose acetate with liquid sulfur dioxid to dissolve the cellulose acetate, and then substantially removing the sulfur .dioxid therefrom with exclusion of moisture.

9. The process of treating a cellulose compound which comprises, subjecting a cellulose ester to the action of liquid sulfur dioxid with exclusion of moisture.

10. The process of treating a cellulose compound which comprises, subjectin a cellulose ester to the action of liquid su fur dloxid with exclusion of molsture, and then substantially-removin the sulfur dioxid.

11. The process 0 treating a cellulose compound which comprises, subjecting cellulose acetate to the action of liquid sulfur dioxid with exclusion of moisture.

12. The process of treating a cellulose compound which comprises, subjecting cellulose acetate to the action of liquid sulfur dioxid with exclusion of moisture, and then substantially removing the sulfur dioxid.

13. The process of treating a cellulose compound which comprises, subjecting a dioxid.

15. The process of treating a cellulose compound which comprises, subjecting cellulose acetate to the action of liquid sulfur dioxid under super-atmospheric pressure.

16. The process of treating a cellu ose compound which comprises, subjecting cellulose acetate to the action of liquid sulfur dioxid under super-atmospheric pressure, and then substantially removing the sulfur dioxid.

17. The process of treating a cellulose compound which comprises, dissolving .a cellulose ester in liquid sulfur dioxid, and then substantially removing the .sulfur dioxid therefrom under a pressure less than that at which the solution was effected.

18. The process of treating a cellulose compound which comprises, dissolving cellulose acetate in liquid sulfur dioxid, and then substantially removing the sulfur dioxid therefrom under a pressure less than that at which the solution was effected.

, 19. The process of treating a cellulose compound which comprises, subjecting a cellulose ester to the action of liquid sulfur dioxid, under super-atmospheric pressure, and then substantlally removing the sulfur dioxid therefrom under a pressure loss than that at which the cellulose ester" was subjectgd to the action of the liquid sulfur diox1 20. The process of treating a cellulose compound which comprises, subjecting cellulose acetate to the action of liquid sulfur dioxid, under super-atmospheric pressure, and then substantially removing the sulfur dioxid therefrom under a pressure less than that at which the cellulose acetate was subjectad to the action of the liquid sulfur diox 21. The process of treating a cellulose compound which comprises, subjecting a cellulose ester to the action of liquid sulfur dioxid, and-then substantially removing the sulfur dioxid therefrom at a pressure less than that at which the treatment was effected and with exclusion of moisture.

22. The process of treating a cellulose compound which comprises, subjecting cellulose acetate to the action or liquid sulfur dioxid, andthen substantially removing the sulfur dioxid therefrom at a pressure less than that at which the treatment was effected and with exclusion of moisture.

23. The pr'ocess of treating a cellulose compound which comprises, subjecting a cellulose ester to the action of liquid su fur dioxid, and then transferring the dissolved material into a menstruum in which the cellulose ester is not initially soluble.

24. The process of treating a cellulose compound which comprises, subjecting a cellulose ester to the action of liquid sulfur dioxid, then transferring the dissolved material into a menstruum in which the cellulose ester is not initially soluble, and subseuently substantially removing the sulfur ioxid. r

25. The process of treating a cellulose compound which comprises, subjecting cellulose acetate to the action of liquid sulfur dioxid, and then transferring the dissolved material into a menstruum in which the cellulose acetate is not initially soluble.

26. The process of treating a cellulose compound which comprises, subjecting cellulose acetate to the action of liquid sulfur dioxid, transferring the dissolved material into a menstruum in which the cellulose acetate is not initially soluble, and subsequently substantially removing the sulfur dioxid.

In testimony whereof I have affixed my signature.

JOHN COLLINS CLANCY. 

